Rapid retreat, acceleration and thinning of Glaciar Upsala, Southern Patagonia Icefield, initiated in 2008

The Patagonia Icefields are characterized by a large number of outlet glaciers calving into lakes and the ocean. In contrast to the recent intensive research activities on tidewater glaciers in other regions, very few observations have been made on calving glaciers in Patagonia. We analysed satellite images of Glaciar Upsala, the third largest freshwater calving glacier in the Southern Patagonia Icefield, to investigate changes in its front position, ice velocity and surface elevation from 2000 to 2011. Our analyses revealed a clear transition from a relatively stable phase to a rapidly retreating and fast-flowing condition in 2008. The glacier front receded by 2.9 km, and the ice velocity increased by 20–50%, over the 2008–11 period. We also found that the ice surface lowered at a rate of up to 39 m a−1 from 2006 to 2010. This magnitude and the rate of changes in the glacier front position, ice velocity and surface elevation are greater than previously reported for Glaciar Upsala, and comparable to recent observations of large tidewater glaciers in Greenland. Our data illustrate details of a rapidly retreating calving glacier in Patagonia that have been scarcely reported despite their importance to the mass budget of the Patagonia Icefields.